You can use a dictionary instead, it's global and you'll have an easier time managing it, then you can save it as json and load it again.
If you insist on using a var, you can use "token", which are separators inside the string:
var score = "43412,43245,12354,12543";
using:
tokenat(score,0,",");
will send you back the first score in the string, 0 is a loopindex number for each token in the string, level1=0, level2=1, level3=2, etc.